[SYNC] Sessions datatype refactor. Most things related to sessions under-the-...

chrome/browser/sync/glue/session_model_associator.cc

Index: chrome/browser/sync/glue/session_model_associator.cc
===================================================================
--- chrome/browser/sync/glue/session_model_associator.cc	(revision 68844)
+++ chrome/browser/sync/glue/session_model_associator.cc	(working copy)
@@ -4,15 +4,19 @@
 
 #include "chrome/browser/sync/glue/session_model_associator.h"
 
+#include <algorithm>
 #include <utility>
 
 #include "base/logging.h"
-#include "base/string_util.h"
-#include "base/utf_string_conversions.h"
+#include "chrome/browser/browser_list.h"
+#include "chrome/browser/browser_window.h"
 #include "chrome/browser/profiles/profile.h"
-#include "chrome/browser/sessions/session_id.h"
 #include "chrome/browser/sync/profile_sync_service.h"
 #include "chrome/browser/sync/syncable/syncable.h"
+#include "chrome/browser/tab_contents/navigation_controller.h"
+#include "chrome/browser/tab_contents/navigation_entry.h"
+#include "chrome/browser/tabs/tab_strip_model.h"
+#include "chrome/common/extensions/extension.h"
 #include "chrome/common/notification_details.h"
 #include "chrome/common/notification_service.h"
 #include "chrome/common/url_constants.h"
@@ -20,94 +24,45 @@
 namespace browser_sync {
 
 namespace {
-
 static const char kNoSessionsFolderError[] =
     "Server did not create the top-level sessions node. We "
     "might be running against an out-of-date server.";
 
+// The maximum number of navigations in each direction we care to sync.
+static const int max_sync_navigation_count = 6;
 }  // namespace
 
-SessionModelAssociator::SessionModelAssociator(
-    ProfileSyncService* sync_service) : sync_service_(sync_service) {
+SessionModelAssociator::SessionModelAssociator(ProfileSyncService* sync_service)
+    : tab_pool_fp_(-1),
+      local_session_syncid_(sync_api::kInvalidId),
+      sync_service_(sync_service) {
   DCHECK(CalledOnValidThread());
   DCHECK(sync_service_);
 }
 
 SessionModelAssociator::~SessionModelAssociator() {
   DCHECK(CalledOnValidThread());
+  DeleteForeignSessions();
 }
 
-bool SessionModelAssociator::AssociateModels() {
-  DCHECK(CalledOnValidThread());
+void SessionModelAssociator::DeleteForeignSessions() {

[tim (not reviewing), 2010/12/15 21:14:00]

should we slap CalledOnValidThread in most of these places?

[Nicolas Zea, 2010/12/16 18:09:18]

Why not.

On 2010/12/15 21:14:00, timsteele wrote:

+  // Delete ForeignSession objects (which also deletes all their windows/tabs).
+  STLDeleteContainerPairSecondPointers(foreign_session_map_.begin(),
+      foreign_session_map_.end());
+  foreign_session_map_.clear();
 
-  // Make sure we have a machine tag.
-  if (current_machine_tag_.empty())
-    InitializeCurrentMachineTag();  // Creates a syncable::BaseTransaction.
+  // Delete IDToSessTab maps. Does not delete the SessionTab objects, because
+  // they should already be referenced through foreign_session_map_.
+  STLDeleteContainerPairSecondPointers(foreign_tab_map_.begin(),
+      foreign_tab_map_.end());
+  foreign_tab_map_.clear();
 
-  {
-    // Do an initial update from sync model (in case we just re-enabled and
-    // already had data).
-    sync_api::ReadTransaction trans(
-        sync_service_->backend()->GetUserShareHandle());
-    UpdateFromSyncModel(&trans);
-  }
-
-  // Check if anything has changed on the client side.
-  UpdateSyncModelDataFromClient();
-  return true;
+  // Go through and delete any tabs we had allocated but had not yet placed into
+  // a ForeignSessionobject.
+  STLDeleteContainerPointers(unmapped_tabs_.begin(), unmapped_tabs_.end());
+  unmapped_tabs_.clear();
 }
 
-bool SessionModelAssociator::ChromeModelHasUserCreatedNodes(
-    bool* has_nodes) {
-  DCHECK(CalledOnValidThread());
-  CHECK(has_nodes);
-  // This is wrong, but this function is unused, anyway.
-  *has_nodes = true;
-  return true;
-}
-
-bool SessionModelAssociator::DisassociateModels() {
-  specifics_.clear();
-
-  // There is no local model stored with which to disassociate, just notify
-  // foreign session handlers.
-  NotificationService::current()->Notify(
-      NotificationType::FOREIGN_SESSION_DISABLED,
-      NotificationService::AllSources(),
-      NotificationService::NoDetails());
-  return true;
-}
-
-const sync_pb::SessionSpecifics* SessionModelAssociator::
-    GetChromeNodeFromSyncId(int64 sync_id) {
-  sync_api::ReadTransaction trans(
-    sync_service_->backend()->GetUserShareHandle());
-  sync_api::ReadNode node(&trans);
-  if (!node.InitByIdLookup(sync_id))
-    return NULL;
-  return new sync_pb::SessionSpecifics(node.GetSessionSpecifics());
-}
-
-bool SessionModelAssociator::GetSyncIdForTaggedNode(const std::string* tag,
-    int64* sync_id) {
-  sync_api::ReadTransaction trans(
-      sync_service_->backend()->GetUserShareHandle());
-  sync_api::ReadNode node(&trans);
-  if (!node.InitByClientTagLookup(syncable::SESSIONS, *tag))
-    return false;
-  *sync_id = node.GetId();
-  return true;
-}
-
-int64 SessionModelAssociator::GetSyncIdFromChromeId(const std::string& id) {
-  sync_api::ReadTransaction trans(
-      sync_service_->backend()->GetUserShareHandle());
-  sync_api::ReadNode node(&trans);
-  if (!node.InitByClientTagLookup(syncable::SESSIONS, id))
-    return sync_api::kInvalidId;
-  return node.GetId();
-}
-
 bool SessionModelAssociator::SyncModelHasUserCreatedNodes(bool* has_nodes) {
   DCHECK(CalledOnValidThread());
   CHECK(has_nodes);
@@ -125,138 +80,190 @@
   return true;
 }
 
-std::string SessionModelAssociator::GetCurrentMachineTag() {
-  DCHECK(!current_machine_tag_.empty());
-  return current_machine_tag_;
+int64 SessionModelAssociator::GetSyncIdFromChromeId(const size_t& id) {
+  return GetSyncIdFromSessionTag(TabIdToTag(id));
 }
 
-void SessionModelAssociator::UpdateSyncModelDataFromClient() {
-  DCHECK(CalledOnValidThread());
-  SessionService::SessionCallback* callback =
-      NewCallback(this, &SessionModelAssociator::OnGotSession);
-  // TODO(jerrica): Stop current race condition, possibly make new method in
-  // session service, which only grabs the windows from memory.
-  GetSessionService()->GetCurrentSession(&consumer_, callback);
+int64 SessionModelAssociator::GetSyncIdFromSessionTag(const std::string& tag) {
+  sync_api::ReadTransaction trans(
+      sync_service_->backend()->GetUserShareHandle());
+  sync_api::ReadNode node(&trans);
+  if (!node.InitByClientTagLookup(syncable::SESSIONS, tag))
+    return sync_api::kInvalidId;
+  return node.GetId();
 }
+void SessionModelAssociator::ReassociateWindows(bool reload_tabs) {
+  sync_pb::SessionSpecifics specifics;
+  specifics.set_session_tag(GetCurrentMachineTag());
+  sync_pb::SessionHeader* header_s = specifics.mutable_header();
 
-// TODO(zea): Don't recreate sessions_ vector from scratch each time. This
-// will involve knowing which sessions have been changed (a different data
-// structure will probably be better too).
-bool SessionModelAssociator::UpdateFromSyncModel(
-    const sync_api::BaseTransaction* trans) {
-  DCHECK(CalledOnValidThread());
+  for (BrowserList::const_iterator i = BrowserList::begin();
+       i != BrowserList::end(); ++i) {
+    // Make sure the browser has tabs and a window. Browsers destructor
+    // removes itself from the BrowserList. When a browser is closed the
+    // destructor is not necessarily run immediately. This means its possible
+    // for us to get a handle to a browser that is about to be removed. If
+    // the tab count is 0 or the window is NULL, the browser is about to be
+    // deleted, so we ignore it.
+    if (ShouldSyncWindowType((*i)->type()) && (*i)->tab_count() &&
+        (*i)->window()) {
+      sync_pb::SessionWindow window_s;
+      SessionID::id_type window_id = (*i)->session_id().id();
+      VLOG(1) << "Reassociating window " << window_id << " with " <<
+          (*i)->tab_count() << " tabs.";
+      window_s.set_window_id(window_id);
+      window_s.set_selected_tab_index((*i)->selected_index());
+      if ((*i)->type() ==
+          Browser::TYPE_NORMAL) {
+        window_s.set_browser_type(
+            sync_pb::SessionWindow_BrowserType_TYPE_NORMAL);
+      } else {
+        window_s.set_browser_type(
+            sync_pb::SessionWindow_BrowserType_TYPE_POPUP);
+      }
 
-  // Rebuild specifics_ vector
-  specifics_.clear();
-  if (!QuerySyncModel(trans, specifics_)) {
-    LOG(ERROR) << "SessionModelAssociator failed to updated from sync model";
-    return false;
+      // Store the order of tabs.
+      bool found_tabs = false;
+      for (int j = 0; j < (*i)->tab_count(); ++j) {
+        TabContents* tab = (*i)->GetTabContentsAt(j);
+        DCHECK(tab);
+        if (IsValidTab(*tab)) {
+          found_tabs = true;
+          window_s.add_tab(tab->controller().session_id().id());
+          if (reload_tabs) {
+            ReassociateTab(*tab);
+          }
+        }
+      }
+      // Only add a window if it contains valid tabs.
+      if (found_tabs) {
+        sync_pb::SessionWindow* header_window = header_s->add_window();
+        *header_window = window_s;
+      }
+    }
   }
 
-  return true;
+  sync_api::WriteTransaction trans(
+      sync_service_->backend()->GetUserShareHandle());
+  sync_api::WriteNode header_node(&trans);
+  if (!header_node.InitByIdLookup(local_session_syncid_)) {
+    LOG(ERROR) << "Failed to load local session header node.";
+    return;
+  }
+  header_node.SetSessionSpecifics(specifics);
 }
 
-bool SessionModelAssociator::QuerySyncModel(
-    const sync_api::BaseTransaction* trans,
-    std::vector<const sync_pb::SessionSpecifics*>& specifics) {
-  DCHECK(CalledOnValidThread());
-  sync_api::ReadNode root(trans);
-  if (!root.InitByTagLookup(kSessionsTag)) {
-    LOG(ERROR) << kNoSessionsFolderError;
-    return false;
+bool SessionModelAssociator::ShouldSyncWindowType(Browser::Type type) {
+  switch (type) {
+    case Browser::TYPE_POPUP:
+      return true;
+    case Browser::TYPE_APP:
+      return false;
+    case Browser::TYPE_APP_POPUP:
+      return false;
+    case Browser::TYPE_DEVTOOLS:
+      return false;
+    case Browser::TYPE_APP_PANEL:
+      return false;
+    case Browser::TYPE_NORMAL:
+    default:
+      return true;
   }
-  sync_api::ReadNode current_machine(trans);
-  int64 current_id = (current_machine.InitByClientTagLookup(syncable::SESSIONS,
-    GetCurrentMachineTag())) ? current_machine.GetId() : sync_api::kInvalidId;
+}
 
-  // Iterate through the nodes and populate the session model.
-  int64 id = root.GetFirstChildId();
-  while (id != sync_api::kInvalidId) {
-    sync_api::ReadNode sync_node(trans);
-    if (!sync_node.InitByIdLookup(id)) {
-      LOG(ERROR) << "Failed to fetch sync node for id " << id;
-      return false;
-    }
-    if (id != current_id) {
-      specifics.insert(specifics.end(), &sync_node.GetSessionSpecifics());
-    }
-    id = sync_node.GetSuccessorId();
+void SessionModelAssociator::ReassociateTabs(
+    const std::vector<TabContents*>& tabs) {
+  for (std::vector<TabContents*>::const_iterator i = tabs.begin();
+       i != tabs.end();
+       ++i) {
+    ReassociateTab(**i);
   }
-  return true;
 }
 
-bool SessionModelAssociator::GetSessionData(
-    std::vector<ForeignSession*>* sessions) {
-  DCHECK(CalledOnValidThread());
+void SessionModelAssociator::ReassociateTab(const TabContents& tab) {
+  if (!IsValidTab(tab))
+    return;
 
-  // Build vector of sessions from specifics data
-  for (std::vector<const sync_pb::SessionSpecifics*>::const_iterator i =
-    specifics_.begin(); i != specifics_.end(); ++i) {
-    // Only include sessions with open windows.
-    if ((*i)->session_window_size() > 0)
-      AppendForeignSessionFromSpecifics(*i, sessions);
+  int64 sync_id;
+  SessionID id(tab.controller().session_id());
+
+  TabLinksMap::const_iterator tablink = tab_map_.find(id);
+  if (tablink == tab_map_.end()) {
+    // This is a new tab, get a sync node for it.
+    sync_id = GetFreeTabNode();
+  } else {
+    // This tab is already associated with a sync node, reuse it.
+    sync_id = tablink->second.sync_id();
   }
+  Associate(&tab, sync_id);
+}
 
-  return true;
+void SessionModelAssociator::Associate(const TabContents* tab, int64 sync_id) {
+  TabLinks t(sync_id, tab);
+  SessionID session_id = tab->controller().session_id();
+  tab_map_[session_id] = t;
+
+  sync_api::WriteTransaction trans(
+      sync_service_->backend()->GetUserShareHandle());
+  WriteTabContentsToSyncModel(*tab, sync_id, &trans);
 }
 
-void SessionModelAssociator::AppendForeignSessionFromSpecifics(
-    const sync_pb::SessionSpecifics* specifics,
-    std::vector<ForeignSession*>* session) {
-  ForeignSession* foreign_session = new ForeignSession();
-  foreign_session->foreign_session_tag = specifics->session_tag();
-  session->insert(session->end(), foreign_session);
-  for (int i = 0; i < specifics->session_window_size(); i++) {
-    const sync_pb::SessionWindow* window = &specifics->session_window(i);
-    SessionWindow* session_window = new SessionWindow();
-    PopulateSessionWindowFromSpecifics(session_window, window);
-    foreign_session->windows.insert(
-        foreign_session->windows.end(), session_window);
+bool SessionModelAssociator::WriteTabContentsToSyncModel(
+    const TabContents& tab,
+    int64 sync_id,
+    sync_api::WriteTransaction* trans) {
+  sync_api::WriteNode tab_node(trans);
+  if (!tab_node.InitByIdLookup(sync_id)) {
+    LOG(ERROR) << "Failed to look up tab node " << sync_id;
+    return false;
   }
-}
 
-// Fills the given vector with foreign session windows to restore.
-void SessionModelAssociator::AppendForeignSessionWithID(int64 id,
-    std::vector<ForeignSession*>* session, sync_api::BaseTransaction* trans) {
-  if (id == sync_api::kInvalidId)
-    return;
-  sync_api::ReadNode node(trans);
-  if (!node.InitByIdLookup(id))
-    return;
-  const sync_pb::SessionSpecifics* ref = &node.GetSessionSpecifics();
-  AppendForeignSessionFromSpecifics(ref, session);
-}
+  sync_pb::SessionSpecifics session_s;
+  session_s.set_session_tag(GetCurrentMachineTag());
+  sync_pb::SessionTab* tab_s = session_s.mutable_tab();
 
-SessionService* SessionModelAssociator::GetSessionService() {
-  DCHECK(sync_service_);
-  Profile* profile = sync_service_->profile();
-  DCHECK(profile);
-  SessionService* sessions_service = profile->GetSessionService();
-  DCHECK(sessions_service);
-  return sessions_service;
-}
+  SessionID::id_type tab_id = tab.controller().session_id().id();
+  tab_s->set_tab_id(tab_id);
+  tab_s->set_window_id(tab.controller().window_id().id());
+  const int current_index = tab.controller().GetCurrentEntryIndex();
+  const int min_index = std::max(0,
+                                 current_index - max_sync_navigation_count);
+  const int max_index = std::min(current_index + max_sync_navigation_count,
+                                 tab.controller().entry_count());
+  const int pending_index = tab.controller().pending_entry_index();
+  Browser* browser = BrowserList::FindBrowserWithID(
+      tab.controller().window_id().id());
+  DCHECK(browser);
+  int index_in_window = browser->tabstrip_model()->GetWrapperIndex(&tab);
+  DCHECK(index_in_window != TabStripModel::kNoTab);
+  tab_s->set_pinned(browser->tabstrip_model()->IsTabPinned(index_in_window));
+  if (tab.extension_app())
+    tab_s->set_extension_app_id(tab.extension_app()->id());
+  for (int i = min_index; i < max_index; ++i) {
+    const NavigationEntry* entry = (i == pending_index) ?
+       tab.controller().pending_entry() : tab.controller().GetEntryAtIndex(i);
+    DCHECK(entry);
+    if (entry->virtual_url().is_valid()) {
+      if (i == max_index-1) {
+        VLOG(1) << "Associating tab " << tab_id << " with sync id " << sync_id
+            << " and url " << entry->virtual_url().possibly_invalid_spec();
+      }
+      TabNavigation tab_nav;
+      tab_nav.SetFromNavigationEntry(*entry);
+      sync_pb::TabNavigation* nav_s = tab_s->add_navigation();
+      PopulateSessionSpecificsNavigation(&tab_nav, nav_s);
+    }
+  }
+  tab_s->set_current_navigation_index(current_index);
 
-void SessionModelAssociator::InitializeCurrentMachineTag() {
-  sync_api::WriteTransaction trans(sync_service_->backend()->
-      GetUserShareHandle());
-  syncable::Directory* dir =
-      trans.GetWrappedWriteTrans()->directory();
-
-  // TODO(zea): We need a better way of creating a machine tag. The directory
-  // kernel's cache_guid changes every time syncing is turned on and off. This
-  // will result in session's associated with stale machine tags persisting on
-  // the server since that tag will not be reused. Eventually this should
-  // become some string identifiable to the user. (Home, Work, Laptop, etc.)
-  // See issue 59672
-  current_machine_tag_ = "session_sync";
-  current_machine_tag_.append(dir->cache_guid());
-  VLOG(1) << "Creating machine tag: " << current_machine_tag_;
+  tab_node.SetSessionSpecifics(session_s);
+  return true;
 }
 
-// See PopulateSessionSpecificsTab for use.  May add functionality that includes
-// the state later.
+// TODO(zea): perhaps sync state (scroll position, form entries, etc.) as well?

[tim (not reviewing), 2010/12/15 21:14:00]

so far we explicitly didn't want to do this but I think we should favor having a
bug instead of a todo to track it

[Nicolas Zea, 2010/12/16 18:09:18]

Done.

 void SessionModelAssociator::PopulateSessionSpecificsNavigation(
-  const TabNavigation* navigation, sync_pb::TabNavigation* tab_navigation) {
+    const TabNavigation* navigation,
+    sync_pb::TabNavigation* tab_navigation) {
   tab_navigation->set_index(navigation->index());
   tab_navigation->set_virtual_url(navigation->virtual_url().spec());
   tab_navigation->set_referrer(navigation->referrer().spec());
@@ -328,125 +335,319 @@
   }
 }
 
-// See PopulateSessionSpecificsWindow for use.
-void SessionModelAssociator::PopulateSessionSpecificsTab(
-  const SessionTab* tab, sync_pb::SessionTab* session_tab) {
-  session_tab->set_tab_visual_index(tab->tab_visual_index);
-  session_tab->set_current_navigation_index(
-      tab->current_navigation_index);
-  session_tab->set_pinned(tab->pinned);
-  session_tab->set_extension_app_id(tab->extension_app_id);
-  for (std::vector<TabNavigation>::const_iterator i3 =
-      tab->navigations.begin(); i3 != tab->navigations.end(); ++i3) {
-    const TabNavigation navigation = *i3;
-    sync_pb::TabNavigation* tab_navigation =
-        session_tab->add_navigation();
-    PopulateSessionSpecificsNavigation(&navigation, tab_navigation);
+void SessionModelAssociator::Disassociate(int64 sync_id) {
+  // TODO(zea): we will need this once we support deleting foreign sessions.

[tim (not reviewing), 2010/12/15 21:14:00]

is it called anywhere?
add a NOTIMPLEMENTED() ?

[Nicolas Zea, 2010/12/16 18:09:18]

Done.

+}
+
+bool SessionModelAssociator::AssociateModels() {
+  DCHECK(CalledOnValidThread());
+
+  // Ensure that we disassociated properly, otherwise memory might leak.
+  DCHECK(foreign_tab_map_.empty());
+  DCHECK(foreign_session_map_.empty());
+
+  // Make sure we have a machine tag.
+  if (current_machine_tag_.empty())
+    InitializeCurrentMachineTag();  // Creates a syncable::BaseTransaction.
+
+  tab_pool_fp_ = -1;
+  local_session_syncid_ = sync_api::kInvalidId;
+
+  // Read any available foreign sessions and load any session data we may have.
+  // If we don't have any local session data in the db, create a header node.
+  {
+    sync_api::WriteTransaction trans(
+        sync_service_->backend()->GetUserShareHandle());
+
+    sync_api::ReadNode root(&trans);
+    if (!root.InitByTagLookup(kSessionsTag)) {
+      LOG(ERROR) << kNoSessionsFolderError;
+      return false;
+    }
+
+    UpdateAssociationsFromSyncModel(root, &trans);
+
+    if (local_session_syncid_ == sync_api::kInvalidId) {
+      // The sync db didn't have a header node for us, we need to create one.
+      sync_api::WriteNode write_node(&trans);
+      if (!write_node.InitUniqueByCreation(syncable::SESSIONS, root,
+          current_machine_tag_)) {
+        LOG(ERROR) << "Failed to create sessions header sync node.";
+        return false;
+      }
+      write_node.SetTitle(UTF8ToWide(current_machine_tag_));
+      local_session_syncid_ = write_node.GetId();
+    }
   }
+
+  // Check if anything has changed on the client side.
+  UpdateSyncModelDataFromClient();
+
+  VLOG(1) << "Session models associated.";
+
+  return true;
 }
 
-// Called when populating session specifics to send to the sync model, called
-// when associating models, or updating the sync model.
-void SessionModelAssociator::PopulateSessionSpecificsWindow(
-  const SessionWindow* window, sync_pb::SessionWindow* session_window) {
-    session_window->set_selected_tab_index(window->selected_tab_index);
-    if (window->type == 1) {
-      session_window->set_browser_type(
-        sync_pb::SessionWindow_BrowserType_TYPE_NORMAL);
-    } else {
-      session_window->set_browser_type(
-        sync_pb::SessionWindow_BrowserType_TYPE_POPUP);
+bool SessionModelAssociator::DisassociateModels() {
+  DeleteForeignSessions();
+  tab_map_.clear();
+  tab_syncid_pool_.clear();
+  tab_pool_fp_ = -1;
+  local_session_syncid_ = sync_api::kInvalidId;
+
+  // There is no local model stored with which to disassociate, just notify
+  // foreign session handlers.
+  NotificationService::current()->Notify(
+      NotificationType::FOREIGN_SESSION_DISABLED,
+      NotificationService::AllSources(),
+      NotificationService::NoDetails());
+  return true;
+}
+
+void SessionModelAssociator::InitializeCurrentMachineTag() {
+  sync_api::WriteTransaction trans(sync_service_->backend()->
+      GetUserShareHandle());
+  syncable::Directory* dir = trans.GetWrappedWriteTrans()->directory();
+
+  // TODO(zea): We need a better way of creating a machine tag. The directory

[tim (not reviewing), 2010/12/15 21:14:00]

reference bug #

[Nicolas Zea, 2010/12/16 18:09:18]

See end of comment paragraph. I went ahead and turned it into a url as well.

On 2010/12/15 21:14:00, timsteele wrote:

+  // kernel's cache_guid changes every time syncing is turned on and off. This
+  // will result in session's associated with stale machine tags persisting on
+  // the server since that tag will not be reused. Eventually this should
+  // become some string identifiable to the user. (Home, Work, Laptop, etc.)
+  // See issue 59672
+  current_machine_tag_ = "session_sync";
+  current_machine_tag_.append(dir->cache_guid());
+  VLOG(1) << "Creating machine tag: " << current_machine_tag_;
+}
+
+bool SessionModelAssociator::UpdateAssociationsFromSyncModel(
+    const sync_api::ReadNode& root,
+    const sync_api::BaseTransaction* trans) {
+  DCHECK(CalledOnValidThread());
+
+  // Iterate through the nodes and associate any foriegn sessions.
+  int64 id = root.GetFirstChildId();
+  while (id != sync_api::kInvalidId) {
+    sync_api::ReadNode sync_node(trans);
+    if (!sync_node.InitByIdLookup(id)) {
+      LOG(ERROR) << "Failed to fetch sync node for id " << id;
+      return false;
     }
-    for (std::vector<SessionTab*>::const_iterator i2 = window->tabs.begin();
-        i2 != window->tabs.end(); ++i2) {
-      const SessionTab* tab = *i2;
-      if (tab->navigations.at(tab->current_navigation_index).virtual_url() ==
-        GURL(chrome::kChromeUINewTabURL)) {
-        continue;
+
+    const sync_pb::SessionSpecifics& specifics =
+        sync_node.GetSessionSpecifics();
+    const int64 modification_time = sync_node.GetModificationTime();
+    if (specifics.session_tag() != GetCurrentMachineTag()) {
+      if (!AssociateForeignSpecifics(specifics, modification_time)) {
+        return false;
       }
-      sync_pb::SessionTab* session_tab = session_window->add_session_tab();
-      PopulateSessionSpecificsTab(tab, session_tab);
+    } else if (id != local_session_syncid_) {
+      // This is previously stored local session information.
+      if (specifics.has_header()) {
+        DCHECK(local_session_syncid_ == sync_api::kInvalidId);
+
+        // This is our previous header node, reuse it.
+        local_session_syncid_ = id;
+      } else {
+        DCHECK(specifics.has_tab());
+
+        // This is a tab node. We want to track these to reuse them in our free
+        // tab node pool. They will be overwritten eventually, so need to do
+        // anything else.
+        tab_syncid_pool_.push_back(id);
+        tab_pool_fp_++;
+      }
     }
+
+    id = sync_node.GetSuccessorId();
+  }
+
+  // After updating from sync model all tabid's should be free.
+  DCHECK(tab_pool_fp_ == static_cast<int64>(tab_syncid_pool_.size())-1);
+
+  return true;
 }
 
-bool SessionModelAssociator::WindowHasNoTabsToSync(
-    const SessionWindow* window) {
-  int num_populated = 0;
-  for (std::vector<SessionTab*>::const_iterator i = window->tabs.begin();
-      i != window->tabs.end(); ++i) {
-    const SessionTab* tab = *i;
-    if (tab->navigations.at(tab->current_navigation_index).virtual_url() ==
-        GURL(chrome::kChromeUINewTabURL)) {
-      continue;
+bool SessionModelAssociator::AssociateForeignSpecifics(
+    const sync_pb::SessionSpecifics& specifics,
+    const int64 modification_time) {
+  std::string foreign_session_tag = specifics.session_tag();
+  DCHECK(foreign_session_tag != GetCurrentMachineTag() ||
+         sync_service_->cros_user() == "test user");  // For tests.
+
+  if (foreign_tab_map_.find(foreign_session_tag) == foreign_tab_map_.end()) {
+    foreign_tab_map_[foreign_session_tag] = new IDToSessTabMap();
+  }
+  if (specifics.has_header()) {
+    // Read in the header data for this foreign session.
+    // Header data contains window information and ordered tab id's for each
+    // window.
+
+    // Load (or create) the ForeignSession object for this client.
+    scoped_ptr<ForeignSession> foreign_session;
+    if (foreign_session_map_.find(foreign_session_tag) !=
+        foreign_session_map_.end()) {
+      foreign_session.reset(foreign_session_map_[foreign_session_tag]);
+    } else {
+      foreign_session.reset(new ForeignSession);
+      foreign_session->foreign_session_tag = foreign_session_tag;
     }
-    num_populated++;
+
+    const sync_pb::SessionHeader& header = specifics.header();
+    foreign_session->windows.reserve(header.window_size());
+    VLOG(1) << "Associating " << foreign_session_tag << " with " <<
+        header.window_size() << " windows.";
+    size_t i;
+    for (i = 0; i < (size_t)header.window_size(); ++i) {
+      if (i >= foreign_session->windows.size()) {
+        // This a new window, create it.
+        foreign_session->windows.push_back(new SessionWindow());
+      }
+      const sync_pb::SessionWindow& window_s = header.window(i);
+      PopulateSessionWindowFromSpecifics(foreign_session_tag,
+                                         window_s,
+                                         modification_time,
+                                         foreign_session->windows[i]);
+    }
+    // Remove any remaining windows (in case windows were closed)
+    for (; i < foreign_session->windows.size(); ++i) {
+      delete foreign_session->windows[i];
+    }
+    foreign_session->windows.resize(header.window_size());
+
+    foreign_session_map_[foreign_session_tag] = foreign_session.release();
+  } else if (specifics.has_tab()) {
+    const sync_pb::SessionTab& tab_s = specifics.tab();
+    SessionID tab_id(tab_s.tab_id());
+    scoped_ptr<SessionTab> tab;
+    if (foreign_tab_map_[foreign_session_tag]->find(tab_id) !=
+        foreign_tab_map_[foreign_session_tag]->end()) {
+      // We've already seen the header for this client, and created the
+      // appropriate tab objects. Go ahead and fill it with the tab info.
+      tab.reset((*foreign_tab_map_[foreign_session_tag])[tab_id]);
+      unmapped_tabs_.erase(tab.get());
+      VLOG(1) << "Associating " << foreign_session_tag << "'s seen tab " <<
+          tab_id.id() << " at " << tab.get();
+    } else {
+      // Create the tab object, and associate it with the tab id in
+      // |foreign_tab_map_|. It will get associated with a window when we
+      // associate the header node for this client.
+      tab.reset(new SessionTab());
+      (*foreign_tab_map_[foreign_session_tag])[tab_id] = tab.get();
+      unmapped_tabs_.insert(tab.get());
+      VLOG(1) << "Associating " << foreign_session_tag << "'s new tab " <<
+          tab_id.id() << " at " << tab.get();
+    }
+    PopulateSessionTabFromSpecifics(tab_s, modification_time, tab.release());
+  } else {
+    NOTREACHED();
+    return false;
   }
-  if (num_populated == 0)
-    return true;
-  return false;
+
+  return true;
 }
 
-void SessionModelAssociator::OnGotSession(int handle,
-    std::vector<SessionWindow*>* windows) {
-  sync_pb::SessionSpecifics specifics;
-  // Set the tag, then iterate through the vector of windows, extracting the
-  // window data, along with the tabs data and tab navigation data to populate
-  // the session specifics.
-  specifics.set_session_tag(GetCurrentMachineTag());
-  FillSpecificsFromSessions(windows, &specifics);
-  bool has_nodes = false;
-  if (!SyncModelHasUserCreatedNodes(&has_nodes))
-    return;
-  if (specifics.session_window_size() == 0 && has_nodes)
-    return;
-  sync_api::WriteTransaction trans(
-      sync_service_->backend()->GetUserShareHandle());
-  sync_api::ReadNode root(&trans);
-  if (!root.InitByTagLookup(kSessionsTag)) {
-    LOG(ERROR) << kNoSessionsFolderError;
-    return;
+void SessionModelAssociator::DisassociateForeignSession(
+    const std::string& foreign_session_tag) {
+  ForeignSessionMap::iterator iter =
+      foreign_session_map_.find(foreign_session_tag);
+  if (iter != foreign_session_map_.end()) {
+    delete iter->second;  // Delete the ForeignSession object.
+    foreign_session_map_.erase(iter);
   }
-  UpdateSyncModel(&specifics, &trans, &root);
 }
 
-void SessionModelAssociator::FillSpecificsFromSessions(
-    std::vector<SessionWindow*>* windows,
-    sync_pb::SessionSpecifics* session) {
-  for (std::vector<SessionWindow*>::const_iterator i = windows->begin();
-      i != windows->end(); ++i) {
-    const SessionWindow* window = *i;
-    if (WindowHasNoTabsToSync(window)) {
-      continue;
+void SessionModelAssociator::PopulateSessionWindowFromSpecifics(
+    std::string foreign_session_tag,
+    const sync_pb::SessionWindow& specifics,
+    int64 mtime,
+    SessionWindow* session_window) {
+  if (specifics.has_window_id())
+    session_window->window_id.set_id(specifics.window_id());
+  if (specifics.has_selected_tab_index())
+    session_window->selected_tab_index = specifics.selected_tab_index();
+  if (specifics.has_browser_type()) {
+    if (specifics.browser_type() ==
+        sync_pb::SessionWindow_BrowserType_TYPE_NORMAL) {
+      session_window->type = 1;
+    } else {
+      session_window->type = 2;
     }
-    sync_pb::SessionWindow* session_window = session->add_session_window();
-    PopulateSessionSpecificsWindow(window, session_window);
   }
+  session_window->timestamp = base::Time::FromInternalValue(mtime);
+  session_window->tabs.resize(specifics.tab_size());
+  for (int i = 0; i < specifics.tab_size(); i++) {
+    SessionID tab_id(specifics.tab(i));
+    scoped_ptr<SessionTab> tab;
+    IDToSessTabMap::iterator iter =
+        foreign_tab_map_[foreign_session_tag]->find(tab_id);
+    if (iter != (*foreign_tab_map_[foreign_session_tag]).end()) {
+      tab.reset(iter->second);
+      unmapped_tabs_.erase(tab.get());
+      VLOG(1) << "Associating " << foreign_session_tag << "'s seen tab " <<
+          tab_id.id()  << " at " << tab.get() << " with window " <<
+          specifics.window_id();
+    } else {
+      tab.reset(new SessionTab());
+      (*foreign_tab_map_[foreign_session_tag])[tab_id] = tab.get();
+      unmapped_tabs_.insert(tab.get());
+      VLOG(1) << "Associating " << foreign_session_tag << "'s new tab " <<
+          tab_id.id()  << " at " << tab.get() << " with window " <<
+          specifics.window_id();
+    }
+    session_window->tabs[i] = tab.release();
+  }
 }
 
+void SessionModelAssociator::PopulateSessionTabFromSpecifics(
+    const sync_pb::SessionTab& specifics,
+    const int64 mtime,
+    SessionTab* tab) {
+  if (specifics.has_tab_id())
+    tab->tab_id.set_id(specifics.tab_id());
+  if (specifics.has_window_id())
+    tab->window_id.set_id(specifics.window_id());
+  if (specifics.has_tab_visual_index())
+    tab->tab_visual_index = specifics.tab_visual_index();
+  if (specifics.has_current_navigation_index())
+    tab->current_navigation_index = specifics.current_navigation_index();
+  if (specifics.has_pinned())
+    tab->pinned = specifics.pinned();
+  if (specifics.has_extension_app_id())
+    tab->extension_app_id = specifics.extension_app_id();
+  tab->timestamp = base::Time::FromInternalValue(mtime);
+  tab->navigations.clear();  // In case we are reusing a previous SessionTab.
+  for (int i = 0; i < specifics.navigation_size(); i++) {
+    AppendSessionTabNavigation(specifics.navigation(i), &tab->navigations);
+  }
+}
+
 void SessionModelAssociator::AppendSessionTabNavigation(
-    std::vector<TabNavigation>* navigations,
-    const sync_pb::TabNavigation* navigation) {
+    const sync_pb::TabNavigation& specifics,
+    std::vector<TabNavigation>* navigations) {
   int index = 0;
   GURL virtual_url;
   GURL referrer;
   string16 title;
   std::string state;
   PageTransition::Type transition(PageTransition::LINK);
-  if (navigation->has_index())
-    index = navigation->index();
-  if (navigation->has_virtual_url()) {
-    GURL gurl(navigation->virtual_url());
+  if (specifics.has_index())
+    index = specifics.index();
+  if (specifics.has_virtual_url()) {
+    GURL gurl(specifics.virtual_url());
     virtual_url = gurl;
   }
-  if (navigation->has_referrer()) {
-    GURL gurl(navigation->referrer());
+  if (specifics.has_referrer()) {
+    GURL gurl(specifics.referrer());
     referrer = gurl;
   }
-  if (navigation->has_title())
-    title = UTF8ToUTF16(navigation->title());
-  if (navigation->has_page_transition() ||
-      navigation->has_navigation_qualifier()) {
-    switch (navigation->page_transition()) {
+  if (specifics.has_title())
+    title = UTF8ToUTF16(specifics.title());
+  if (specifics.has_state())
+    state = specifics.state();
+  if (specifics.has_page_transition() ||
+      specifics.has_navigation_qualifier()) {
+    switch (specifics.page_transition()) {
       case sync_pb::TabNavigation_PageTransition_LINK:
         transition = PageTransition::LINK;
         break;
@@ -487,7 +688,7 @@
         transition = PageTransition::CHAIN_END;
         break;
       default:
-        switch (navigation->navigation_qualifier()) {
+        switch (specifics.navigation_qualifier()) {
           case sync_pb::
               TabNavigation_PageTransitionQualifier_CLIENT_REDIRECT:
             transition = PageTransition::CLIENT_REDIRECT;
@@ -506,67 +707,293 @@
   navigations->insert(navigations->end(), tab_navigation);
 }
 
-void SessionModelAssociator::PopulateSessionTabFromSpecifics(
-    SessionTab* session_tab,
-    const sync_pb::SessionTab* tab, SessionID id) {
-  session_tab->window_id = id;
-  SessionID tabID;
-  session_tab->tab_id = tabID;
-  if (tab->has_tab_visual_index())
-    session_tab->tab_visual_index = tab->tab_visual_index();
-  if (tab->has_current_navigation_index()) {
-    session_tab->current_navigation_index =
-    tab->current_navigation_index();
+void SessionModelAssociator::UpdateSyncModelDataFromClient() {
+  DCHECK(CalledOnValidThread());
+  // TODO(zea): the logic for determining if we want to sync and the loading of
+  // the previous session should go here. We can probably reuse the code for
+  // loading the current session from the old session implementation.
+  // SessionService::SessionCallback* callback =
+  //     NewCallback(this, &SessionModelAssociator::OnGotSession);
+  // GetSessionService()->GetCurrentSession(&consumer_, callback);
+
+  // Associate all open windows and their tabs.
+  ReassociateWindows(true);
+}
+
+int64 SessionModelAssociator::GetFreeTabNode() {
+  if (tab_pool_fp_ == -1) {
+    // Tab pool has no free nodes, allocate new one.
+    sync_api::WriteTransaction trans(
+        sync_service_->backend()->GetUserShareHandle());
+    sync_api::ReadNode root(&trans);
+    if (!root.InitByTagLookup(kSessionsTag)) {
+      LOG(ERROR) << kNoSessionsFolderError;
+      return 0;
+    }
+    size_t tab_node_id = tab_syncid_pool_.size();
+    std::string tab_node_tag = TabIdToTag(tab_node_id);
+    sync_api::WriteNode tab_node(&trans);
+    if (!tab_node.InitUniqueByCreation(syncable::SESSIONS, root,
+                                       tab_node_tag)) {
+      LOG(ERROR) << "Could not create node for session " <<
+          GetCurrentMachineTag();
+      return -1;
+    }
+    tab_node.SetTitle(UTF8ToWide(tab_node_tag));
+
+    // Grow the pool by 1 since we created a new node. We don't actually need
+    // to put the node's id in the pool now, since the pool is still empty.
+    // The id will be added when that tab is closed and the node is freed.
+    tab_syncid_pool_.resize(tab_node_id + 1);
+    VLOG(1) << "Adding sync node " << tab_node.GetId() << " to tab syncid pool";
+    return tab_node.GetId();
+  } else {
+    // There are nodes available, grab next free and decrement free pointer.
+    return tab_syncid_pool_[static_cast<size_t>(tab_pool_fp_--)];
   }
-  if (tab->has_pinned())
-    session_tab->pinned = tab->pinned();
-  if (tab->has_extension_app_id())
-    session_tab->extension_app_id = tab->extension_app_id();
-  for (int i3 = 0; i3 < tab->navigation_size(); i3++) {
-    const sync_pb::TabNavigation* navigation = &tab->navigation(i3);
-    AppendSessionTabNavigation(&session_tab->navigations, navigation);
+}
+
+void SessionModelAssociator::FreeTabNode(int64 sync_id) {
+  // Pool size should always match # of free tab nodes.
+  DCHECK(tab_pool_fp_ < static_cast<int64>(tab_syncid_pool_.size()));
+  tab_syncid_pool_[static_cast<size_t>(++tab_pool_fp_)] = sync_id;
+}
+
+bool SessionModelAssociator::GetAllForeignSessions(
+    std::vector<const ForeignSession*>* sessions) {
+  DCHECK(CalledOnValidThread());
+
+  // Build vector of sessions from our foreign session map.
+  for (ForeignSessionMap::const_iterator i =
+    foreign_session_map_.begin(); i != foreign_session_map_.end(); ++i) {
+    // Only include sessions with open tabs.
+    ForeignSession* foreign_session = i->second;
+    if (foreign_session->windows.size() > 0 &&
+        !WindowHasNoTabsToSync(*foreign_session->windows[0]))
+      sessions->push_back(foreign_session);
   }
+
+  return true;
 }
 
-void SessionModelAssociator::PopulateSessionWindowFromSpecifics(
-    SessionWindow* session_window, const sync_pb::SessionWindow* window) {
-  SessionID id;
-  session_window->window_id = id;
-  if (window->has_selected_tab_index())
-    session_window->selected_tab_index = window->selected_tab_index();
-  if (window->has_browser_type()) {
-    if (window->browser_type() ==
-        sync_pb::SessionWindow_BrowserType_TYPE_NORMAL) {
-      session_window->type = 1;
-    } else {
-      session_window->type = 2;
+bool SessionModelAssociator::GetForeignSession(
+    const std::string& tag,
+    std::vector<SessionWindow*>* sessions) {
+  DCHECK(CalledOnValidThread());
+
+  ForeignSessionMap::iterator iter = foreign_session_map_.find(tag);
+  if (iter == foreign_session_map_.end())
+    return false;
+  *sessions = iter->second->windows;
+
+  return true;
+}
+
+bool SessionModelAssociator::GetForeignTab(
+    const std::string& tag,
+    const SessionID::id_type tab_id,
+    const SessionTab** tab) {
+  if (foreign_tab_map_.find(tag) == foreign_tab_map_.end())
+    return false;
+  SessionID id(tab_id);
+  if (foreign_tab_map_[tag]->find(id) == foreign_tab_map_[tag]->end())
+    return false;
+  *tab = (*foreign_tab_map_[tag])[id];
+  return true;
+}
+
+bool SessionModelAssociator::WindowHasNoTabsToSync(
+    const SessionWindow& window) {
+  int num_populated = 0;
+  for (std::vector<SessionTab*>::const_iterator i = window.tabs.begin();
+      i != window.tabs.end(); ++i) {
+    const SessionTab* tab = *i;
+    if (IsValidSessionTab(*tab))
+      num_populated++;
+  }
+  if (num_populated == 0)
+    return true;
+  return false;
+}
+
+// Valid local tab?
+bool SessionModelAssociator::IsValidTab(const TabContents& tab) {
+  if ((tab.profile() == sync_service_->profile() ||
+       sync_service_->profile() == NULL)) {
+    const NavigationEntry* entry = tab.controller().GetActiveEntry();
+    if (!entry)
+      return false;
+    if (entry->virtual_url().is_valid() &&
+        (entry->virtual_url() != GURL(chrome::kChromeUINewTabURL) ||
+         tab.controller().entry_count() > 1)) {
+      return true;
     }
   }
-  for (int i = 0; i < window->session_tab_size(); i++) {
-    const sync_pb::SessionTab& tab = window->session_tab(i);
-    SessionTab* session_tab = new SessionTab();
-    PopulateSessionTabFromSpecifics(session_tab, &tab, id);
-    session_window->tabs.insert(session_window->tabs.end(), session_tab);
+  return false;
+}
+
+// Valid foreign tab?
+bool SessionModelAssociator::IsValidSessionTab(const SessionTab& tab) {
+  if (tab.navigations.empty())
+    return false;
+  int selected_index = tab.current_navigation_index;
+  selected_index = std::max(
+      0,
+      std::min(selected_index,
+          static_cast<int>(tab.navigations.size() - 1)));
+  if (selected_index == 0 &&
+      tab.navigations.size() == 1 &&
+      tab.navigations.at(selected_index).virtual_url() ==
+          GURL(chrome::kChromeUINewTabURL)) {
+    // This is a new tab with no further history, skip.
+    return false;
   }
+  return true;
 }
 
-bool SessionModelAssociator::UpdateSyncModel(
-    sync_pb::SessionSpecifics* session_data,
-    sync_api::WriteTransaction* trans,
-    const sync_api::ReadNode* root) {
-  const std::string id = session_data->session_tag();
-  sync_api::WriteNode write_node(trans);
-  if (!write_node.InitByClientTagLookup(syncable::SESSIONS, id)) {
-    sync_api::WriteNode create_node(trans);
-    if (!create_node.InitUniqueByCreation(syncable::SESSIONS, *root, id)) {
-      LOG(ERROR) << "Could not create node for session " << id;
+// ==========================================================================
+// The following methods are not currently used but will likely become useful
+// if we choose to sync the previous browser session.

[tim (not reviewing), 2010/12/15 21:14:00]

previous? is there a bug#?

[Nicolas Zea, 2010/12/16 18:09:18]

No, should I make one? this refers to what Travis was mentioning, wherein we may
at some point want to sync previous browser sessions if we see that there are no
open tabs (ie the browser crashed or user quit). We didn't know if we were
planning to do this though.

On 2010/12/15 21:14:00, timsteele wrote:

+
+SessionService* SessionModelAssociator::GetSessionService() {
+  DCHECK(sync_service_);
+  Profile* profile = sync_service_->profile();
+  DCHECK(profile);
+  SessionService* sessions_service = profile->GetSessionService();
+  DCHECK(sessions_service);
+  return sessions_service;
+}
+
+void SessionModelAssociator::OnGotSession(
+    int handle,
+    std::vector<SessionWindow*>* windows) {
+  DCHECK(local_session_syncid_);
+
+  sync_pb::SessionSpecifics specifics;
+  specifics.set_session_tag(GetCurrentMachineTag());
+  sync_pb::SessionHeader* header_s = specifics.mutable_header();
+  PopulateSessionSpecificsHeader(*windows, header_s);
+
+  sync_api::WriteTransaction trans(
+      sync_service_->backend()->GetUserShareHandle());
+  sync_api::ReadNode root(&trans);
+  if (!root.InitByTagLookup(kSessionsTag)) {
+    LOG(ERROR) << kNoSessionsFolderError;
+    return;
+  }
+
+  sync_api::WriteNode header_node(&trans);
+  if (!header_node.InitByIdLookup(local_session_syncid_)) {
+    LOG(ERROR) << "Failed to load local session header node.";
+    return;
+  }
+
+  header_node.SetSessionSpecifics(specifics);
+}
+
+void SessionModelAssociator::PopulateSessionSpecificsHeader(
+    const std::vector<SessionWindow*>& windows,
+    sync_pb::SessionHeader* header_s) {
+
+  // Iterate through the vector of windows, extracting the window data, along
+  // with the tab data to populate the session specifics.
+  for (size_t i = 0; i < windows.size(); ++i) {
+    if (WindowHasNoTabsToSync(*(windows[i])))
+      continue;
+    sync_pb::SessionWindow* window_s = header_s->add_window();
+    PopulateSessionSpecificsWindow(*(windows[i]), window_s);
+    if (!SyncLocalWindowToSyncModel(*(windows[i])))
+      return;
+  }
+}
+
+// Called when populating session specifics to send to the sync model, called
+// when associating models, or updating the sync model.
+void SessionModelAssociator::PopulateSessionSpecificsWindow(
+    const SessionWindow& window,
+    sync_pb::SessionWindow* session_window) {
+  session_window->set_window_id(window.window_id.id());
+  session_window->set_selected_tab_index(window.selected_tab_index);
+  if (window.type == Browser::TYPE_NORMAL) {
+    session_window->set_browser_type(
+      sync_pb::SessionWindow_BrowserType_TYPE_NORMAL);
+  } else if (window.type == Browser::TYPE_POPUP) {
+    session_window->set_browser_type(
+      sync_pb::SessionWindow_BrowserType_TYPE_POPUP);
+  } else {
+    // ignore
+    LOG(WARNING) << "Session Sync unable to handle windows of type" <<
+        window.type;
+    return;
+  }
+  for (std::vector<SessionTab*>::const_iterator i = window.tabs.begin();
+      i != window.tabs.end(); ++i) {
+    const SessionTab* tab = *i;
+    if (!IsValidSessionTab(*tab))
+      continue;
+    session_window->add_tab(tab->tab_id.id());
+  }
+}
+
+bool SessionModelAssociator::SyncLocalWindowToSyncModel(
+    const SessionWindow& window) {
+  DCHECK(tab_map_.empty());
+  for (size_t i = 0; i < window.tabs.size(); ++i) {
+    SessionTab* tab = window.tabs[i];
+    int64 id = GetFreeTabNode();
+    if (id == -1) {
+      LOG(ERROR) << "Failed to find/generate free sync node for tab.";
       return false;
     }
-    create_node.SetSessionSpecifics(*session_data);
-    return true;
+
+    sync_api::WriteTransaction trans(
+        sync_service_->backend()->GetUserShareHandle());
+    if (!WriteSessionTabToSyncModel(*tab, id, &trans)) {
+      return false;
+    }
+
+    TabLinks t(id, tab);
+    tab_map_[tab->tab_id] = t;
   }
-  write_node.SetSessionSpecifics(*session_data);
   return true;
 }
 
+bool SessionModelAssociator::WriteSessionTabToSyncModel(
+    const SessionTab& tab,
+    const int64 sync_id,
+    sync_api::WriteTransaction* trans) {
+  sync_api::WriteNode tab_node(trans);
+  if (!tab_node.InitByIdLookup(sync_id)) {
+    LOG(ERROR) << "Failed to look up tab node " << sync_id;
+    return false;
+  }
+
+  sync_pb::SessionSpecifics specifics;
+  specifics.set_session_tag(GetCurrentMachineTag());
+  sync_pb::SessionTab* tab_s = specifics.mutable_tab();
+  PopulateSessionSpecificsTab(tab, tab_s);
+  tab_node.SetSessionSpecifics(specifics);
+  return true;
+}
+
+// See PopulateSessionSpecificsWindow for use.
+void SessionModelAssociator::PopulateSessionSpecificsTab(
+    const SessionTab& tab,
+    sync_pb::SessionTab* session_tab) {
+  session_tab->set_tab_id(tab.tab_id.id());
+  session_tab->set_window_id(tab.window_id.id());
+  session_tab->set_tab_visual_index(tab.tab_visual_index);
+  session_tab->set_current_navigation_index(
+      tab.current_navigation_index);
+  session_tab->set_pinned(tab.pinned);
+  session_tab->set_extension_app_id(tab.extension_app_id);
+  for (std::vector<TabNavigation>::const_iterator i =
+      tab.navigations.begin(); i != tab.navigations.end(); ++i) {
+    const TabNavigation navigation = *i;
+    sync_pb::TabNavigation* tab_navigation =
+        session_tab->add_navigation();
+    PopulateSessionSpecificsNavigation(&navigation, tab_navigation);
+  }
+}
+
 }  // namespace browser_sync